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# WAEC GCE Nov/Dec 2018 Chemistry Practical Expo Answer Welcome to the Real and Verified WAEC GCE Chemistry Practical Questions and Answer – Nov/Dec 2018 Expo Runz.

(1ai)
Tabulate:
Burette reading |1 |2 |3 |
vol of acid used|24.80|24.00|24.10|
(1aii) Average volume of A used
Va = 24.00 + 24.10/2
= 24.05cm^3
(1bi)
Concentration of A in moldm^-3
A contains 0.79g of KMnO4 per 250cm³ of solution.
Hence since 250cm³ = 0.79g
100cm³ = Xg
X = 1000×0.79/250 = 3.16g
Hence Conc in g/dm³ of A = 3.16gdm^-³
But molar conc = mass conc(gdm^-³)/molar mass(g/mol)
Hence molar Conc.Of A= 3.16gdm^-3/molar mass ofA
But molar mass of A = KMnO4
= 39 + 55 + 4(16) = 39 + 55 + 64
= 158g/mol
Hence Conc in moldm^-³ of A = 3.16gdm^-3/158g/mol
= 0.020moldm^-3
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2)
A is ZnSO4(aq)
B is NaOH(aq)
C is Pb(NO3)2 (aq)
D is HCL(aq)
Reasons
ROW 1
it is used to distinguish Pb from Zn since both behave alike with NAPth
It gives a white precipitate with Pb^2+ ions but not with Zn^2+. The first
row obviously shows that. Also there actually no visible reaction whne Itcl (A) and NaOlt are mixed(C)
Row 2
when A and B mirces, the products Zncl2 and
H2SO4 one soluble hence no visible reaction
is scene Between B and D, a white precipitate is seen because PbaS04 insoluble
Between B and C, Zn^2+ On yield a white gelatinous precipate with NaOlta
—————————————————————-
Question 3
a(i) Sodium is stored under paraffin oil to prevent its oxidation by atmospheric gases
(ii) desiccator lid must be greased with a thin layer of grease, to ensure an airtight seal.
(iii)
b(i)
(ii) Dip a rod in aqueous Ammonia and dip in a beaker containing the acids, only HCl produces dense white fumes of ammonium chloride
c(i) Beaker, glass rod, volumetric flask
(ii) A gas which smells like that of burning(SO2) matches evolves
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2)
A is ZnSO4(aq)
B is NaOH(aq)
C is Pb(NO3)2 (aq)
D is HCL(aq)